Raising Awareness and the Use of Different Irrigation Strategies to Promote

Water Efficiency During Drought Miriam Morua and Emily Wieber

Plants &Water Lab, Department of Biological Science

California State University Fullerton

Effect of RDI on Navel Orange Physiology and Yield

Introduction

Comparing Surface vs. Subsurface Irrigation on Peppers

New Study: To Find the Best Plant-Based

Method for Avocado Irrigation

Strategies to Conserve Water

• California is currently in a drought crisis due to lack of rainfall, low snow pack melting, and diminished groundwater levels.

• About 80% of the state‘s water goes to irrigation. CA is the biggest farm state in the United States ($447 billion a year).

• Drought is known to limit plant productivity and alters biochemical and physiological processes. This will lead to increased water costs and

ultimately high food prices.

• Efficient irrigation methods, such as regulated deficit irrigation (RDI) and drip irrigation (DI), can reduce water use in agriculture such as

avocado and citrus orchards (Goldhamer et al., 2000).

• The goal of this research is to raise awareness regarding the use of water-saving irrigation strategies. The intention is to promote, inform

and motivate students, staff, faculty, and the public to consider using the water-saving strategies presented in this research project for their

personal gardening in their homes.

• Previous studies have shown that these irrigation strategies can increase productivity while reducing water usage.

• Regulated deficit irrigation (RDI) application during the

early fruit growth and fruit ripening phases can save

water without compromising fruit yield.

• The research objective was to measure the plant’s

physiological responses and fruit yield when the trees

were subjected to RDI.

• Navel orange trees were subjected to a control, RDI1,

RDI2, and RDI3.

Fig.2: Irrigation Setup for 1.2 Acre of Navel Orange Trees at UC Riverside Citrus Experiment Station

• The orange trees irrigated 25% less during the fall, their

fruit yield and quality remained the same as irrigated at

100%.

• Although smaller fruits were watered less, the fruit

sweetness remained the same as those irrigated at 100%.

• Surface irrigation (SDI) involves slow dripping of water on the

surface of the soil by emitters that carry a low flow of water under

low pressure to plants. It is adaptable and minimizes water loss

through runoff.

• Subsurface irrigation (SSDI) involves delivering water directly to

the root systems by burying the drip tape underground. It reduces

water loss due to evaporation, runoff, and wind drift but it is more

expensive and labor intensive.

• The research objective was to investigate whether there was a

difference between (SDI & SSDI) to assess the efficiency of water

management by comparing soil moisture retention,

photosynthesis, and yields.

• Peppers irrigated with subsurface irrigation had higher

productivity (lbs) and stomatal conductance (mmol/s2) compared

to surface while maintaining higher levels of soil moisture content.

Fig.1: An Update on Dramatic Reduction in Percent Normal Precipitation

• Current efficient irrigation scheduling mostly relies on

atmospheric and soil-water data but these are often

unreliable (Geerts et al, 2009).

• Alternative indirect continuous measures of plant water

need may help conserve water.

• The research objective is to identify the best measure of

water stress for avocado trees to guide irrigation by

comparing direct soil-based measures to indirect plant-

based measures.

• The goal of this new study is to promote better water

management practices that can be applicable to other

orchards.

• Using RDI reduces water usage by 20% (Wieber, 2014).

• SSDI retained 25% more water compared to subsurface

(Morua, 2012).

• Simply by installing a water meter to monitor water use in

residency can cut down water usage by 25% as mandated

by Gov. Jerry Brown (Fresno Water District, 2015).

Geerts, S., Raes, D., 2009. Agric. Water Manag. 96, 1275–1284.

Goldhamer D.A. & Salinas M. 2000. Proc. Int. Soc. Citricult. IX. 227-231

Figure 4: Subsurface irrigation set up (left) and surface irrigation set up (right) at the

Fullerton Arboretum.

Figure 3: Schematic of irrigation set up for both methods.

Treatment Yield

(kg/tree)

Number

of

Fruit/Tree

Percentage of Weight Distribution of Different Fruit Size Across Treatments

Juice

Brim A

Very Tiny

50 – 59

mm

Tiny

60 – 63.4

mm

X-Small

63.5 –

68.9 mm

Small

69 – 74.9

mm

Medium

75 – 80

mm

Large

81 – 88

mm

X-Large

> 88

mm

Control 47.70 a 192 a .5 a 4.2 a 12.8 a 19.5 ab 25.9 a 20.3 a 5.6 a 10.85 a

RDI1 35.83 b 163 a 1.0 a 9.4 a 18.6 a 13.7 a 11.0 b 10.6 ab 2.6 a 10.81 a

RDI2 52.18 ab 212 a 1.2 a 5.7 a 20.9 a 26.1 b 28.8 a 14.2 ab 3.1 a 11.04 a

RDI3 42.22 ab 192 a 1.4 a 10.1 a 21.1 a 21.3 ab 13.1 b 7 b 4.9 a 11.17 a

Table 1: Effect of irrigation treatment on fruit yield and fruit size